Active ingredient components useful as a pesticide, such as insecticides, fungicides and herbicides, have been prepared into formulations, such as wettable powders and dusts, depending upon their physicochemical properties and the objective to use them practically in agricultural crop fields. A wettable powder and a dust can be formulated by admixing a solid active component useful as a pesticide, inorganic mineral carriers and surface active agents and subsequently allowing the mixture to a process of dry milling. The particle size is in a range of from 5 to 10 .mu.m, so there is a problem of securing safety on human bodies, such as powder inhalation problem at the time of measuring a powder formulation to dilute with water. In order to solve such problem as described above, a water dispersible granule which is manufactured according to extrusion method has been developed recently.
The water dispersible granule produced according to the extrusion method is manufactured by admixing a solid active component useful as a pesticide, a carrier composed of mineral fine powder, a surfactant, etc., adding bound water after the dry milling process, kneading by using a kneader, and subsequently forcing the kneaded-material to pass through a plate having holes with a diameter of from 0.5 to 1.0 mm.
However, the production of the water dispersible granule by means of dry milling process could not be made in cases that the pesticidal active component has a low melting point and therefore it is not suitable for the dry milling, or in case that it is necessary to further allow the active substance to a fine milling in order to enhance its biological activity.
Therefore, when producing the water dispersible granule according to the extrusion method where a pesticidal active component either having a low melting point and therefore not being applicable for dry milling process or being required to be subjected to fine pulverization process for enhancing its biological activity, it was necessary in the past to allow the active substance to wet millimg process and then to kneading granulation process in combination with a carrier composed of mineral materials.
On the other hand, from the same purpose as described above, a method to firstly make the active substance to a slurry state by means of wet milling process, then to mix the slurry with a carrier of minerals and finally to allow the mixture to the extrusion process to obtain granules has been developed. For example, in Japanese Patent Laid-open No. Hei 3-146126 Gazette, a method to improve the dispersibility at milling and the granulation property by adding a small amount of sodium alkylnaphthalenesulfonate during the process of wet milling is disclosed. However, there is still a problem that wet milling of the active substance might be not possible sometime depending upon the chemical property of the active substance itself, due to the lowering of dispersibility of sodium alkylnaphthalenesulfonate.